Inorganic particulate materials are commonly blended with polymeric materials to form composite materials. For example, such inorganic particulate materials may be blended with thermoset polymers to form thermally-stable high-strength polymer composites. In another example, such inorganic particulate materials may be blended with curable elastomeric resins to form reinforced elastomeric composites.
As such, inorganic particulate materials may be used as filler and may function as reinforcements, colorants, or radiation absorbers. For example, zirconia and titania are commonly used as whitening agents and ultraviolet radiation absorbers. In another example, carbon black is typically used to form dark composites that withstand ultraviolet radiation. In a particular example, inorganic particulate materials are used in elastomeric composites for manufacturing tires. In addition to carbon black, precipitated silica is often used to provide low rolling resistance, for example, to reduce gas consumption, and wet surface traction.
In order to reduce fuel consumption, attempts have been made by tires producers to obtain tires with low rolling resistance. In addition, tire manufacturers have desire improved grip on both on wet and dry conditions, and wear resistance. As such, manufacturers have typically turned to a sulfur-vulcanizable diene rubber composition obtained by thermo-mechanical working of a conjugated diene copolymer and an aromatic vinyl compound, and reinforced with special highly dispersible precipitated silica. Highly dispersible precipitated silica is made of spherical primary particles, which are aggregated together. These primary particles typically have a low aspect ratio, generally around 1.
The so called “green tires” have had a significant commercial success in passenger car market in Europe and more recently in North America. However the development of green tires for trucks has been more difficult due to a lower wear resistance than conventional truck tire reinforced mainly with carbon black.
Turning to aluminous materials, nano-boehmite particles can be easily dispersed into a nylon polymer matrix due to the high surface compatibility between the boehmite material and the highly polar polymer matrix. However, nano-boehmite particles are difficulty to disperse in a non-polar matrix, such a diene rubber composition for a tire formulation. In general, higher aspect ratio nano-boehmite particles are more difficult to disperse in rubber.
Numerous solutions have been proposed to improve the dispersion of inorganic nano-particles with high aspect ratio in non polar polymers. For example, organic surface treatment agents that modify the surface chemistry of the particles to make it more compatible with the polymer have been proposed. Such an approach, for example, has been used to disperse nano-clay in Nylon or polypropylene using quaternary ammonium as an organic surface treatment agent. However, even with the organic agents, it is often difficult to achieve desirable dispersion of such inorganic particulate, especially if the filler loading is high (more than 10% per volume). Moreover, in the case of tire formulation, an organic surface treatment may not be desirable. For example, it may be desirable for the surface of the reinforcing fillers to react with a polysulfurized silane coupling agent during the compounding process, and thus can not be passivated by the organic surface treatment agent.
As such, a dispersible filler and composite material formed thereof would be desirable.